The present invention relates to an arrangement for regulating the supercharger air pressure in a combustion engine operated with exhaust gas supercharge, which is equipped with an exhaust gas turbosupercharger consisting of a supercharger and an exhaust gas turbine; the regulating arrangement consists of a valve controlling an exhaust gas bypass to the exhaust gas turbine; this valve has a pressure unit which is divided by a diaphragm into two chambers, with the diaphragm on one side exposed to the supercharger air pressure, and on the other side to the force of a spring.
Vehicle engines require a maximum torque during maximum acceleration at low engine speeds. To achieve this, the exhaust gas supercharger is constructed so that it produces high turbine speeds even at low engine speeds. At high engine speeds, part of the exhaust gas flow is no longer delivered to the exhaust gas turbosupercharger so that the supercharger air pressure is limited.
Such an arrangement is known from the German Laid-Open Document 23 62 133. It discloses a valve controlling the exhaust gas bypass to the exhaust gas turbine; this valve has a pressure unit which is divided by a diaphragm into two chambers, with the diaphragm being exposed to supercharger air pressure in the opening direction and to force the compression spring in the closing direction. In one embodiment the diaphragm receives a controlled supercharger pressure in order to shift the opening point of the exhaust gas bypass valve towards a higher supercharger pressure. In a second embodiment the membrane is exposed to a controlled supercharger air pressure in the opening direction, and to the force of a compression spring and atmospheric pressure in the other direction. Both designs require a spring of high initial force--combined with a small valve design--to keep the valve closed until reaching the desired upper supercharger pressure. After attaining this supercharger pressure, the spring must be capable of opening the exhaust gas bypass valve and to open and close it even with small pressure changes on the supercharger pressure side in order to continuously adjust to the desired supercharger pressure.
This means that the spring, with the desired small height, has a high initial spring force when installed and a very gentle spring characteristic for regulating. These opposite requirements cannot be met by a spring produced by mass production.
Hence it is an object of the present invention to provide an exhaust gas control valve which meets the requirements regarding opening point and regulating behavior within narrow limits, and allows the use of a simple commercial compression spring.
Another object of the present invention is to provide an arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide an arrangement, as described, which may be readily maintained in service and which has a substantially long operating life.